This invention relates to an induction system for an engine and more particularly to an improved induction system particularly adapted for use with V type engines.
It is well known that the design of the induction system for an internal combustion engine is extremely important in determining the performance of the engine. One common type of induction system employed for engines employs one or more plenum chambers, each of which serves respective cylinders through individual intake passages that extend from the plenum chamber to the intake ports of the engine. This type of induction system has been found to be extremely effective and provide good engine performance. However, the use of such plenum chambers and intake passages, particularly when plural plenum chambers are employed, can present problems in conjunction with the overall engine package. Both the size of the plenum chambers and the length of in the intake passages connecting them to the intake ports are determinative of the engine performance. It is, of course, desirable to provide a very compact engine. This can dictate both the size and location of the plenum chambers.
It is, therefore, a principal object of this invention to provide an improved, compact induction system for an internal combustion engine.
It is a further object of this invention to provide an induction system for an internal combustion engine embodying plenum chambers and interconnecting intake passageways serving intake ports from the plenum chambers and incorporating a compact and yet efficient system.
When plural plenum chambers are employed, it is frequently the practice to have each plenum chamber serve alternately firing cylinders of the engine so that the flow from the plenum chamber to the individual cylinders can be uniform. However, when the plenum chambers are interconnected, each to alternately firing chambers, certain problems can arise. That is, it may be difficult to provide the necessary interconnecting passageways while, at the same time, maintaining uniform length for each of the intake passages. It is important to insure substantially uniform length for the intake passages so that the charging efficiency for each cylinder will be the same.
It is, therefore, a still further object of this invention to provide an improved induction system for an internal combustion engine including at least two plenum chambers, each of which serves different cylinders of the engine and wherein the length of the intake passages interconnecting the plenum chambers with the cylinders are all substantially the same length.
In conjunction with the use of plural plenum chambers for an engine, it is advisable to position the plenum chamber in close proximity to the cylinders of the engine. When the engine is of the V type, it is desirable to position the plenum chambers in the valley between the banks of cylinders. However, this further complicates the problems as aforedescribed.
It is, therefore, a further object of this invention to provide an improved induction system for a V type engine embodying separate plenum chambers for respective cylinder of the engine.
With respect to the provision of an induction system of the engine, performance at a given speed and/or load range can be improved by tuning the length of the intake passages and the relative volumes of the plenum chambers. However, an induction system that is tuned to provide maximum performance at one running condition will not necessarily provide good performance at other running conditions. In order to obviate these difficulties, it has been proposed to employ an induction system for an engine that employs two different length runners for serving each cylinder of the engine. One runner is tuned for high speed performance and the other is tuned for lower or mid range performance. Obviously, the use of two runners complicates the induction system and further makes it difficult to meet the aforenoted objectives.
It is, therefore, a still further object of this invention to provide an improved, compact two stage induction system for an internal combustion engine.
When compound or staged induction systems are employed for engines, it is the practice to provide some form of throttling in one of the intake passages so that it will serve the cylinders only under the running condition for which it is tuned. Where multiple cylinders are employed, it is desirable to insure that all throttle valves of the same intake passages are operated simultaneously. One easy way that this can be done is to provide a single throttle valve shaft on it which all of these throttle valves are supported. However, with the type of induction systems previously proposed, the throttle valve shaft must pass through substantially all of the induction passages of the engine, regardless of whether or not there is a throttle valve in the respective induction passage, due to the layout of the engine. This obviously is detrimental, can reduce air flow and can complicate sealing.
It is, therefore, a still further object of this invention to provide an improved compound or staged induction system wherein a plurality of throttle valves can be operated simultaneously without interfering with the induction passages in which throttle valves are not required.
As a further complication, with respect to the positioning of the intake passages for a compound or staged induction system, it is necessary in some instances to provide long intake passages having a greater flow resistance and in some instances to provide shorter passages having lesser flow resistance. It is, therefore, a still further object of this invention to provide an induction system that provides such staging while maintaining a compact engine configuration.
It has been previously noted that in conjunction with the induction systems for V type engines, it is desirable to make the engine more compact by providing the plenum chambers for the engine in the valley between the cylinder banks. However, frequently it is desirable to position engine driven accessories in this same area. This can interfere with the desired size of the plenum chamber and also with the positioning of the intake passages that connect the plenum chamber to the individual cylinders.
It is, therefore, a still further object of this invention to provide an improved induction system for a V type engine including plenum chambers positioned in the valley between the banks of cylinders and wherein the plenum chambers do not extend for the full length of the engine so as to accommodate accessories also in the valley of the engine.